The present invention relates to a method and solvent for use in extracting oil from oil bearing materials, preferably a triglyceride rich oil is selectively extracted from the oil bearing material. More preferably, the present invention relates to a solvent, comprised of a hydrocarbon and a fluorocarbon, and a method that will preferably remove an amount of oil comprised of greater than 95% by weight triglycerides and other non-polar constituents from an oil bearing material, such as a soybean material.
Oils, especially oils comprised primarily of triglycerides and other non-polar constituents, are used in a variety of applications including uses as edible and non-edible oils. Edible oils that are high in triglycerides are especially desired and are typically used as food ingredients or as a medium for frying or cooking foods. Triglyceride rich edible oils are preferred for use because they have a high smoke temperature, meaning they do not readily smoke or burn when heated, making them ideal for frying or cooking, and have a desirable flavor. It should be pointed out that most edible oils sold in grocery stores are primarily comprised of triglycerides. Non-edible oils include technical oils such as lubricating oils and hydraulic fluids and fuel.
There are a variety of sources available for use in extracting oils which are high in triglycerides. Some of the available raw material sources include: soybeans, corn, sunflower, palm, cotton seed, olives, peanuts, linseed, and coconut. Additionally, there are other types of vegetable and animal matter which can be used to extract oil that is high in triglycerides. Regardless of the source of the oil, it is generally preferred that the extracted oil be devoid of unsaponifiable matter, pigments, phospholipids or phosphatides, and odoriferous components. This is especially true if the oil is going to be used for cooking or edible oil purposes. Unfortunately, most known methods for extracting oil from oil bearing materials initially result in an oil which contains these unwanted components. As such, it is often necessary to pass the extracted oil through a number of refining steps to ensure adequate removal of the odoriferous components, phospholipids, and pigments. Additional refining steps, however, are undesirable because additional steps generally raise the cost associated with producing both edible and non-edible oils. Increased energy inputs are required and often more equipment is necessary. For these reasons, it is desired to have a more cost efficient and less energy intensive method which most likely requires fewer steps for removing oils rich in triglycerides from oil bearing materials.
Of particular interest is an oil rich in triglycerides derived or extracted from soybeans. It is known that soybean oils are especially prevalent for use in cooking and, in general, are desired for use as an edible oil. Soybean oils are especially well known for use in frying foods. Before selling soybean oil commercially for use in cooking, it is necessary to ensure that the phospholipid, color, and odoriferous constituents are removed, otherwise consumers will consider the product undesirable for consumption and cooking uses. This is especially true if the oil has a disagreeable smell as a result of the odoriferous compounds. For this reason, it is especially desired to have a more efficient, less energy intensive method for extracting triglyceride rich soybean oil from soybean material.
Traditionally, soybeans and other oil bearing materials have had oils extracted by a general method which includes preparation of the oil bearing material, extraction of the oil from the oil bearing material with an organic solvent, separation of the solvent from the oil, and removal of polar materials, including phospholipids, pigments, odor, and color constituents from the oil. This is generally followed by a solvent neutralization step. It is known that in this general process, the step for removal of the polar materials, such as the phospholipids, pigments, and odoriferous constituents, and the solvent neutralization step can add costs and result in increased energy inputs. What is greatly desired is a method that allows for extraction of a triglyceride rich oil from an oil bearing material, especially soybeans, that does not initially remove the phospholipids, pigments, or odoriferous compounds with the triglyceride rich oil. It is also desired if a solvent neutralization step is not required. In other words, it is greatly desired to have a solvent and/or a method that selectively extracts triglycerides from the oil bearing material and that does not result in the extraction of the odoriferous compounds, color constituents, and phospholipids with the triglycerides.
A number of processes exist for extracting oils from oil bearing material; however, a vast majority of these known methods are disadvantageous for one reason or another. For example, it is well-known in the extraction art to use hexane to extract triglyceride rich oil from oil bearing materials. This, however, suffers from two problems. First, the extracted oil contains a sufficient amount of phospholipids, odoriferous components, and color components so as to warrant additional steps necessary to remove these constituents. Hexanes alone do not selectively extract triglyceride rich oil. This, in turn, increases the amount of energy and number of pieces of equipment required to separate the oil from the oil bearing material and, as such, increases the cost. The second problem is that hexanes are highly flammable and has been known to combust and cause plant explosions. However, the majority of soy oil extraction methods use hexane, because hexanes have a low viscosity and most oil components are miscible in hexane. As such, it is desired to have a method and/or solvent that preferably includes the use of hexane for removing the oil from the oil bearing materials which does not require an additional removal step for the color, odor, and phospholipid constituents, and which is non-flammable or, more particularly, less hazardous to human health.
It is further desired to be able to extract the oil in conditions that are close to ambient. It is even more preferred to be able to separate the oil from the solvent at ambient or near ambient conditions. This is desired because of the lesser energy input required. Currently, many removal processes include a distillation step designed to separate the solvent from the oil. As such, it is especially desired to eliminate or reduce the need for a distillation step from the oil extraction method.
It has been known to use a mixture of solvents, including hydrocarbons and halogenated hydrocarbons, to extract oil from an oil bearing material. It is believed that the known solvent mixtures typically have a higher polarity than the oil. The use of a higher polarity solvent appears to have developed into the preferred way for extracting oils from oil bearing material. In general, it appears that the art has taught away from lowering the polarity of the solvent to produce a solvent having a polarity of about 0 or less than that of the oil. Instead, the art, as observed by currently practiced methods, has apparently taught that the highly non-polar solvents are not suitable for extracting non-polar triglycerides.
In U.S. Pat. No. 4,008,210, invented by Steele, et al., a potential use of a mixed solvent is disclosed. Specifically, the method disclosed in the Steele patent relates to the formation of a proteinaceous material that is devoid of oil components, with the method unrelated to the selective extraction of triglycerides. Importantly, the method does not disclose how to selectively extract a triglyceride rich oil from an oil bearing composition. Further, this patent does not disclose the specific requirements for a solvent that will selectively extract triglycerides from oil bearing materials at near ambient conditions.
Thus, it is desired to have a substantially safe, nonhazardous solvent and/or method for selectively extracting triglycerides from oil bearing materials, especially soybeans, that requires very little energy input and that, in particular, can be conducted at near ambient conditions. It is especially desired to have a method and/or solvent that results in the selective extraction of oil that is preferably comprised of 95% or greater triglycerides and non-polar constituents, and even more preferably, comprised of 99% or more triglycerides so that phospholipid, color, and odoriferous constituents do not have to be separated from the oil after removal of the solvent.
The present invention relates to a solvent which can be used in the extraction of oil from oil bearing materials. Preferably, the solvent will result in the selective extraction of an oil comprised of at least 95% by weight non-polar constituents. Even more preferred is for the solvent to selectively extract an oil comprised of greater than 99% by weight non-polar constituents, including triglycerides. Additionally, a method can be used with the present solvent to extract the oil from the oil bearing material.
Besides resulting in a selective extraction, the solvent will have a sufficiently low viscosity so as to allow it to readily pass over or through the oil bearing material. In particular, the solvent will not have a viscosity such that the viscosity is a rate limiting factor in the extraction of the oil from the oil bearing material. With this in mind, it is preferred for the solvent to have a viscosity equal to or less than about 2.6 centipoise. Further, because it is desired to extract an oil comprised primarily of non-polar constituents, it is necessary for the solvent to have a polarity that is equal to or less than the non-polar constituents. In particular, the polarity should be equal to or less than the polarity of the triglycerides which primarily comprise the oil. As such, it is preferred for the solvent to have a polarity that is equal to or less than 0.1. Additionally, the solvent is relatively non-flammable, has a low toxicity or is not overly hazardous to human health, and does not result in causation of significant ozone depletion.
Any of a variety of constituents can be used to form the solvent; however, it has been found that a solvent having the above characteristics can be formed by combining or mixing an organic halide or non-polar halogenated solvent, generally a fluorocarbon, with a low molecular weight hydrocarbon. Preferably, the hydrocarbon will be of the formula CnH(2n+2), or CnH2n and 3, with n equal to between 5 and 8. Even more preferred is for the hydrocarbon to be a hexane.
The fluorocarbon is preferably selected from the group consisting of hydrofluorocarbon, perfluorocarbon, chlorofluorocarbon, hydrochlorofluorocarbon, hydrochlorocarbon, and combinations thereof. More preferably, the fluorocarbon will be a hydrofluorocarbon, a perfluorocarbon, or a hydrochlorofluorocarbon. Hydrofluorocarbon is presently the most preferred fluorocarbon for use with the hydrocarbon. The fluorocarbon constituents that are desired are non-hazardous, non-flammable, have a polarity of less than 0.1, and can be used to form a solvent that will selectively extract an oil that is rich in triglycerides and other non-polar constituents. Also, the selected fluorocarbon should have a boiling point below the boiling point of a triglyceride but above ambient temperatures. Obviously, other fluorocarbon constituents can be used, however, they may suffer from being hazardous, for example. The hydrocarbon and fluorocarbon can be mixed together in any of a variety of amounts so long as the mixture of constituents results in a solvent that has a viscosity of less than 2.6 centipoise and a polarity less than about 0.1. When a hydrocarbon, such as hexane, is mixed with a fluorinated hydrocarbon, or fluorocarbon, such as decafluoropentane, the fluorinated hydrocarbon will typically comprise about 65% by volume of the solvent.
As mentioned, the solvent can be used as part of a method to extract oil from oil bearing materials, with the method initiated by preparing the oil bearing materials for extraction. The preparation begins by making sure that the oil bearing materials are of a sufficient size so as to expose as much as possible of the surface area of the oil bearing materials to the solvent without clogging the device used to expose the oil bearing materials to the solvent. After preparation of the oil bearing materials, the method involves exposing such materials to the solvent. It should be noted, that the temperature in which the oil is extracted from the oil bearing materials should range between about 35xc2x0 C. and about 55xc2x0 C. Such a temperature will result in the oil being miscible in the solvent. This is preferably done in a device that causes the solvent and oil bearing materials to move counter to one another so that there is sufficient contact between the solvent and the oil bearing materials. Once sufficient contact has been made between the solvent and the oil bearing materials, a solvent and oil mixture will be formed, also known as a miscella. It is then preferred to separate the solvent and oil mixture from the oil bearing materials.
After separation of the oil and solvent mixture, or miscella, from the oil bearing materials, it is necessary to then cool the miscella to a temperature ranging between about 15xc2x0 C. and about 25xc2x0 C. so as to cause formation of two distinct layers. The oil can then be easily separated from the solvent so that an oil is formed which is nonhazardous to human health and is ready for immediate use as an edible oil. The separated oil is comprised of greater than 95% by weight non-polar constituents.
The present invention is advantageous for a number of reasons. First, the present invention requires a comparatively lesser amount of energy input than other known methods, meaning the present solvent and method result in a comparatively cheaper extraction of oil. Additionally, the present invention is advantageous because a selective extraction occurs which eliminates the need for additional refining steps designed to remove polar constituents, including unwanted constituents such as odoriferous compounds, color components, and phospholipids. A further advantage is that the present invention is easily performed, meaning application takes a lesser amount of time and energy than what is believed to be involved in other oil extraction methods. Yet another advantage is that the solvent and method are comparatively safe for human use and are non-hazardous. Advantageously, the solvent and method result in the extraction of greater than 15%, preferably 20%, of the total soybean material, which is comparable to other presently used methods for extracting oil from oil bearing materials.